The $16.60 per hour Ms. Ramos earns as a janitor at Apple works out to about the same in inflation-adjusted terms as what Ms. Evans earned 35 years ago. But that’s where the similarities end.

Ms. Evans was a full-time employee of Kodak. She received more than four weeks of paid vacation per year, reimbursement of some tuition costs to go to college part time, and a bonus payment every March. When the facility she cleaned was shut down, the company found another job for her: cutting film.

Ms. Ramos is an employee of a contractor that Apple uses to keep its facilities clean. She hasn’t taken a vacation in years, because she can’t afford the lost wages. Going back to school is similarly out of reach. There are certainly no bonuses, nor even a remote possibility of being transferred to some other role at Apple.

Yet the biggest difference between their two experiences is in the opportunities they created. A manager learned that Ms. Evans was taking computer classes while she was working as a janitor and asked her to teach some other employees how to use spreadsheet software to track inventory. When she eventually finished her college degree in 1987, she was promoted to a professional-track job in information technology.

Many of today’s jobs are grease and cogs in the greater wheels. Those jobs won’t last as robotics pick up the slack in many areas of work. What to do then?